Tension actuator having constraining sleeve immersed in a single layer of elastomeric material

ABSTRACT

The tubular component of a fluid-driven tension actuator is made in a two layer system wherein a woven sleeve is immersed in a tubular shaped elastomeric material.

BACKGROUND OF THE INVENTION

[0001] 1. Technical Field

[0002] The present invention is generally concerned with high pressure fluid-driven tension actuators. It is particularly concerned with the construction of the tubular components of such actuators.

[0003] 2. Description of Related Art

[0004] Tension actuators convert fluid pressure input into mechanical movement output. More specifically, they convert fluid pressure input into linear contraction and linear extension. For example, U.S. Pat. No. 4,751,869 teaches such a high pressure fluid-driven tension actuator. It is comprised of a resilient, hollow, tubular bladder that, when inflated, has an enlarged, generally spherical, central portion. The bladder component of the actuator is encompassed by a contour knitted, fabric sleeve which provides constraining meridians and parallels to the bladder when it is inflated. The knitted sleeve reinforces the bladder against rupture upon inflation by a high pressure fluid such as compressed air. The sleeve also serves to define an outer limit to radial expansion of the tubular bladder. The tubular bladder and the knitted sleeve are bonded together with a bonding material that is cured and thereby forming an integrally bonded structure. The bonding material can be a latex compound, neoprene or silicon rubber.

[0005] U.S. Pat. No. 4,733,603 teaches an axially contractible actuator having a hollow enclosure with an opening for admitting a pressurized fluid such as compressed air. The hollow enclosure is encompassed by a radially expandable, axially contractible constraining means that contains the hollow enclosure when it is inflated. In one preferred embodiment of this invention, the constraining means comprises a network of non-stretchable, flexible tension links.

[0006] U.S. Pat. No. 4,819,547 teaches an actuator comprised of a hollow tubular enclosure having at least one opening for admitting a pressurized fluid such as compressed air. The enclosure is surrounded by a constraining net-like system. This system is comprised of a network of non-stretchable flexible links extending about the enclosure. The links may be, for example, flexible braided wire covered with a plastic material.

[0007] U.S. Pat. No. 4,841,845 teaches a pneumatic drive device which is comprised of a hermetically-sealable chamber, which is bounded by a wall made from a substantially resiliently distortable material and flexible but substantially unstretchable spiral-wound filaments such as steel wires which extend, next to one another, in the form of a casing about the wall.

[0008] U.S. Pat. No. 5,351,602 teaches an air muscle having a longitudinally inflexible, radially expandable sleeve for containing a pressurized bladder of elastic material. The bladder enlarges diametrically when pressured and bulges the wall of the sleeve outward. This causes the sleeve to contract axially.

[0009] U.S. Pat. No. 4,751,868 teaches a fluid-driven twister-pair which turns into various angular positions in response to changes in pressure of the pressurized fluid being fed into the twister-pair. The elastic shells into which air is forced in order to effect a turning action is made of a single ply elastic material.

[0010] U.S. Pat. No. 4,008,008 teaches a pump having a resiliently deformable chamber associated with a controlling means which deforms the chamber by expansion and retraction. The resiliently deformable chamber is encased in a rigid wall chamber.

[0011] U.S. Pat. No. 3,915,010 teaches a bellows for use in high pressure environments. The bellows has a closed end with a conical, internal core and an open end that is secured about a bulb-shaped fitting. The bellows is used in a bore hole pressure measuring system.

[0012] U.S. Pat. No. 3,924,519 teaches an actuating device formed from an elastic tub having circumferential reinforcement and having a portion of the periphery provided with longitudinal cords of tension resistant material along only one side of the tubing. In its relaxed state, the device is substantially linear, but upon introduction of a pressurized fluid such as air the tube curls about the side having the longitudinally reinforced cords. Upon release of the pressurized fluid, the device turns to a substantially linear state.

[0013] U.S. Pat. No. 2,940,772 teaches an amplifying device for pilot operating valves. The amplifying member includes a support member and an annular diaphragm. The support member has an annular, outwardly facing groove with a rounded inner groove wall for receiving the inner portion of the diaphragm. Said diaphragm has opposed surfaces which are freely moveable in the groove and cornered inner edges for engaging the rounded inner groove wall.

[0014] U.S. Pat. No. 3,601,442 teaches a gripping device comprised of a plurality of closed end “fingers” of elastic tubing extending from a common pressure manifold. Each finger has a portion of the traverse wall section provided with longitudinal cords of tension resistant material embedded therein along only one side of the tubing. In the relaxed state the fingers are substantially linear, but upon introduction of pressurized fluid the fingers curl toward a common central region for gripping. Upon release of the pressurized fluid, the elastomeric fingers of the device return to a substantially linear state and thereby releasing the grip.

SUMMARY OF THE INVENTION

[0015] The present invention provides novel tension actuators and methods for constructing them. Such actuators employ tubular or semi-spherical bodies comprised of a constraining sleeve that is immersed in an elastomeric resilient material. The sleeve has left and right strands of meridian and parallel type elements of a woven or knitted construction that allow it to axially expand. In effect, applicant's sleeve is embedded in an elastomeric, resilient, material having a generally tubular or semi-spherical configuration. The outside of the resulting tubular or semi-spherical body defines both the radial extent of the outside surface of the body and the radial extent of a fluid chamber that is present inside the body. Each end of the tubular or semi-spherical body is sealed by a plug to enable said bodies to serve as an air tight pressure chamber. So employed, the woven or knitted constraining elements reinforce the tube or semi-sphere against rupture and serve to limit spherical expansion of the tube or semi-spherical body to a desired limit. The energy for the actuator to return to its initial tubular shape is derived from both the counteractive forces of the elastomeric material and the woven or knitted sleeve material.

[0016] In some of the more preferred embodiments of this invention, the elastomeric material will be a latex compound, a neoprene compound or a silicon compound. The strands that make up the sleeve's woven or knitted construction are preferably made of a strong, tough, flexible material that is capable of being formed into strands. Synthetic yarn material such as Dacron® and fibers such as hemp are especially useful for applicant's purposes. Preferably, the end plugs and end plug accessory attachments of this patent disclosure are made of a strong, rigid plastic such as polycarbonate, acetal resin, nylon, high density polypropylene, Delrin® and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 depicts a cut-away side view of a fluid-driven tension actuator in its unactuated state.

[0018]FIG. 1A is a cut-away side view of a fluid-driven tension actuator in its unactuated state wherein the tubular component of said actuator has a bulged configuration in its center region.

[0019]FIG. 2 depicts the fluid-driven tension actuator of FIG. 1 in its actuated state.

[0020]FIG. 2A depicts the fluid-driven tension actuator of FIG. 1A in its actuated state.

[0021]FIG. 3 is a cross-sectional view of a prior art fluid-driven tension actuator tube.

[0022]FIG. 4 is a perspective end view of the tension actuator tube of FIG. 3.

[0023]FIG. 5 is a cut-away side view of another prior art tension actuator tube.

[0024]FIG. 6 is a perspective end view of the tension actuator tube of FIG. 5.

[0025]FIG. 7 is a cut-away side view of a tension actuator tube made according to the teachings of this patent disclosure.

[0026]FIG. 8 is a perspective view of the tension actuator tube of FIG. 7.

[0027]FIG. 9 is a side view of woven sleeve or knitted component of a tension actuator of the present invention in its unactuated state.

[0028]FIG. 10 is a side view of the woven sleeve component of FIG. 9 in its actuated state.

[0029]FIG. 11 is an exploded, perspective view of an actuator tube, end plug and end plug accessory of this patent disclosure.

[0030]FIGS. 12A to 12K show end plug devices of this patent disclosure combined with various accessory plugs.

[0031]FIG. 13 shows a end plug provided with a coupling device in the form of a cable system that extends to, and is combined at, the forward end of an end plug.

[0032]FIG. 14 is a perspective view of the end plug and cable system of FIG. 13.

DETAILED DESCRIPTION OF THE INVENTION

[0033]FIG. 1 depicts a fluid-drive tension actuator 10. It is generally comprised of a tubular body 12 having a left end plug 14 and a right end plug 16. The left end plug 14 is shown provided with a fitting 18 having a hole for introducing a pressured gas such as compressed air into the interior 12′ of the tubular body 12. The fitting 18 also can be used to release gas from the tubular body 12. End plug 14 is also shown provided with a connector device 20 for mechanically connecting the end plug 14, and hence the actuator 10, to a cable, linkage arm, etc. (not shown) that is actuated/deactuated by the linear motion of the tension actuator 10. An end plug 16 on the right end of the tubular body 12 also is shown provided with a fitting 22 for introducing a pressured gas such as compressed air into the tubular body. This fitting 22 can be used to release gas from the interior 12′ of the tubular body 22 as well. This end plug 16 is also provided with a mechanical connector device 24. In its unactuated state, the device 10 generally extends between lines 26 and 28, i.e., it has a length 30 as measured from the outside end of the left plug 14 to the outside end of the right plug 16.

[0034]FIG. 2 depicts the fluid-driven tension actuator 10 of FIG. 1 in its actuated, or “pumped up” state. A pressurized gas such as compressed air has been forced into the interior region 12′ of the tubular body 12. This causes the actuator 10 to bulge outward in the radial or axial directions generally indicated by arrows 32 and 34. This bulging of the tube 12 causes the left end of the left plug 14 to be drawn inward in the direction generally indicated by arrow 36. The left end of plug 14 is shown as having come to rest at a position 38 that lies inside line 26. Similarly, the right end of plug 16 is drawn inward in the manner suggested by arrow 40. It is shown as having reached a position 42 that lies inside line 28. Thus, the length 44 of the actuated device 10 is less than the length 30 of the unactuated device. This linear contraction in the length of the tension actuator 10 can be “harnessed” and used to pull on mechanical devices such as cables, linkage arms, fasteners, etc. that are attached to connectors 20 and/or 24 and thereby create substantially linear mechanical actions that can be put to use. That is to say that a mechanical device (e.g., a cable, linkage arm, etc.) that is connected to connector 20 and/or connector 24 will experience a tension force by virtue of the fact that the length of the actuator 10 being shortened from its unactuated length 30 to its actuated length 44. A counter mechanical action is created when the actuator 10 is returned to its original length 30 when the compressed gas is released from the interior 12′ of the tube 12.

[0035]FIG. 1A depicts a tension actuator 10 that is very similar to the actuator 10 shown in FIG. 1. The only difference is the fact that the actuator of FIG. 1A has a tubular body that has a bulged center region in its unactuated state. That is to say that this center region of this tubular body is permanently axially or radially expanded.

[0036]FIG. 2A depicts the fluid-driven tension actuator 10 of FIG. 1A in its actuated, “pumped up” or further radially expanded state. In this state, the actuator takes on a more sphere-like configuration. The linear movement of action is again depicted as the difference between the unactuated length 30 and the actuated length 44.

[0037]FIG. 3 is a cross sectional view of a prior art tension actuator tube 46. The actuator tube 46 is comprised of three layers of material. The inner layer 48 is an elastomeric tubular material that forms the inside of the tube 46. The second layer 50 also is an elastomeric material that adheres to a woven sleeve device 52 that surrounds the second layer 50 which, in turn, surrounds the inner layer 48. Thus, the woven sleeve device 52 serves as both the outermost layer of the tension actuator tube and as the primary means by which radial expansion of the actuator tube 46 is limited.

[0038]FIG. 4 is a perspective view of the tension actuator tube 46 shown in FIG. 3. It shows how the three layers 48, 50 and 52 are arranged in concentric circles about the center of the actuator tube 46. A pressured gas is injected and exhausted into and out of the chamber 54 in order to axially expand the tube 46 and thereby linearly contract the actuator tube 46. FIG. 4 also shows the woven nature of the sleeve device 52. That is to say it is comprised of rightwardly directed strands 52(A), 52(B), 52(C), etc. and interwoven leftwardly directed strands 52(D), 52(E), 52(F), etc.

[0039]FIG. 5 is a side view of another prior art tension actuator tube 56. It is comprised of an inner layer 58, an outer layer 60 and a sleeve 62. The outer layer 60 is an elastomeric material in which the sleeve 62 is immersed or embedded. Thus, this actuator tube 56 also can be regarded as having three layers.

[0040]FIG. 6 is a perspective view of the tension actuator tube 56 shown in FIG. 5. It particularly emphasizes that the sleeve 62 is immersed in the outer layer 60. It also shows and emphasizes that the resulting tube 56 has three layers of material: (1) an inner layer 58, an outer layer 60 and a sleeve 62.

[0041]FIG. 7 is a cut-away side view of a tension actuator tube 64 made according to the teachings of this patent disclosure. The tube 64 has a chamber 66 that is surrounded by two types of material. The first type of material 68 is an elastomeric material that serves as both the inner layer and the outer layer of the tube 64. A sleeve 70 is shown immersed in this elastomeric material 68. Since the elastomeric material 68 permeates the open spaces of the woven or knitted sleeve, the elastomeric material can be regarded as being a unified body of material. Thus, this tube has two layers (i.e., an elastomeric material layer 68 and a sleeve 70). This circumstance contrasts with the actuator systems shown in FIGS. 3 and 5 which have three distinct layers. Moreover, the sleeve 70 does not protrude through the outside surface 76 of the tube 64 as it does in the prior art device depicted in FIG. 3. Nor does it protrude through the inside surface 78 of the tube 64. In some of the more preferred embodiments of this invention, the sleeve 70 is located near the center of the elastomeric material 68 that forms the tube 64. This circumstance is depicted in FIG. 7, by showing the distance 72 between the sleeve 70 and the outside surface 76 of the tube 64 to be substantially the same as the distance between the sleeve 70 and the inside surface 78 of the tube 64.

[0042]FIG. 8 is a perspective view of the tension actuator tube 64 shown in FIG. 7. This view emphasizes that the tube 64 is comprised of two layers of material: a layer of elastomeric material 68 and a sleeve 70 that is immersed or embedded in the body of elastomeric material 70. As is better shown in FIGS. 9 and 10 the sleeve 70 also is of a woven or knitted construction.

[0043]FIG. 9 depicts the sleeve 70 component of the tube 64 shown in FIGS. 7 and 8. This sleeve 70 component is shown in its unactuated state (e.g., when the chamber 66 shown in FIGS. 7 and 8 is not under pressure). For the sake of illustration only, this sleeve 70 is depicted as having a simple woven construction. Other, more complex, woven or knitted construction patterns known to the weaving arts can be used as well. By way of example only, weave patterns or networks known as “plain knit” patterns or as “close mesh” networks can be employed in the sleeves used in the tubular components of the tension actuators of this patent disclosure. In any case, the simple woven construction shown in FIG. 7 will be used as applicant's pictorial example. It includes a leftwardly (L) directed array of strands 70L(1), 70L(2), 70L(3), etc. that is interwoven, in an “over and under” fashion, with a rightwardly (R) directed array of strands 70R(1), 70R(2), 70R(3), etc. Such leftward (L) and rightward (R) arrays also may be thought as being meridians and parallels, especially when the tube is in its axially expanded state. Moreover, the net or mesh 12 of the tubular sleeve 70 is preferably circumferentially continuous in the same manner as the wall of a stocking or sock, i.e., being cut only at its axial ends. The sleeve 70 is preferably knit from a strand of the constituent fiber in what is generally known as a continuous tubular knit pattern. The benefits of the use of this pattern are explained in U.S. Pat. No. 4,751,869. Consequently, its teachings are hereby incorporated into the present patent disclosure.

[0044] In the tube's unactuated state, this simple woven construction creates an array of relatively small inter-strand regions 70H(1), 70H(2), 70H(3), etc. But for the presence of the elastomeric material, these inter-strand regions would be holes or open space. In the tension actuators of this patent disclosure, these holes are completely filled, or permeated, by the elastic material 68. Thus, the elastomeric material 68 extends from the outer surface 76 of the tube 64 shown in FIGS. 7 and 89, permeates the inter-strand regions 70H(1), 70H(2), 70H(3), etc. of the sleeve weave and extends to the inner surface 78 of the tube 64.

[0045]FIG. 10 depicts the sleeve 70 component of the tube 64 shown in FIGS. 7 and 8 in a radially or axially extended state such as that shown in FIG. 2. In this extended state, the leftwardly (L) directed array of strands 70L(1), 70L(2), 70L(3), etc. and the rightwardly (R) directed strands 70R(1), 70R(2), 70R(3) are forced in the radial directions suggested by arrows 80 and 82. In doing this, the weave or knit is “opened up” such that the inter-strand regions 70H(1)′, 70H(2)′, 70H(3)′, etc. become larger. Nonetheless these inter-strand regions are still permeated by the elastomeric material 68. That is to say that, while being a component of a tube such as that shown in FIG. 7, the elastomeric material 68 in these inter-strand regions 70H(1)′, 70H(2)′, 70H(3)′, etc. has been stretched by the radial expansion 80, 82 of the tube sleeve 70.

[0046] The term “strand” also is intended to include an elongated continuous element made from a desired fiber and suitable for knitting. Thus, for example, a “strand” may mean a thread, cord, string, filament, line, yarn, twine, or the like. The strand in the ends sections of the sleeve 70 are preferably relatively more tightly knitted with a uniform size of relatively small knitting loops. Therefore, these end sections are relatively constricted, having a relatively small uniform diameter. The strand in the central more spherical section is preferably more loosely knitted, giving this section a consequently larger diameter.

[0047] The end plugs for the actuators of this patent disclosure can be in the form of a single piece or multiple pieces. Such a single piece can be provided with both a gas inlet/vent opening and one or more mechanical connector devices (e.g., a ring for receiving a cable or linkage arm). By way of example only, plugs having such a single piece design are shown in FIGS. 1 and 2. FIG. 11, however, illustrates a more preferred embodiment of this invention wherein the actuator device is provided with an end plug that is comprised of two or more distinct components. The first component is a end plug piece 84 that has a first end 86 that is inserted into the actuator's chamber 66 and affixed to the inside surface 78 of the tube 64. Preferably, this first end 86 has a grooved surface 88 (such as that presented by machine threads) that is capable of making a biting or gripping contact with the inside surface of the tube (e.g., surface 78 of tube 64 in FIG. 7). This gripping contact may be aided by the use of adhesives. Therefore, this first end 86 of the end plug piece 84 will preferably have an outside diameter that creates a compression fit against the inside surface 78 of the tube 64. This compression fit can be aided by use of a compression gripping device 89 known to these arts. Such a device 89 compressedly encompasses the outside surface 76 of the end of the tube 64 into which the first end 86 of the end plug piece 84 has been inserted. The compression gripping device 89 includes a bolt-operated tightening device 91. The opposite end of the end plug piece 84 is preferably provided with a coupling mechanism. Such a coupling mechanism, for example, could be an inside threaded hole or an outside threaded post. By way of example, FIG. 11 shows the end plug piece 84 provided with an inside threaded hole 90.

[0048] Thus, such a coupling device 90 can be used to couple a variety of different accessory attachments to the end plug piece 84. Such an accessory attachment is depicted as item 92 in FIG. 11. Generally speaking such an accessory attachment 92 will provide (1) a mechanical device (e.g., a post 94 having threads 96) for attaching the accessory attachment 92 to the end plug piece 84, (2) an inlet/outlet passage device 98 for injecting and/or exhausting a compressed gas into and/or out of the chamber 66 defined by the tube 64 and its two end plugs and (3) a connector device 100 (rings, hooks, fasteners, connector devices, etc. known to the mechanical arts) for attaching cables, linkage arms, lever arms, etc. to the accessory attachment 92. These connector devices, in turn, can be used to control a wide variety of mechanical operations. They are, however, especially useful in toys and animated figures used to create animated characters or objects for motion pictures.

[0049] FIGS. 12A-12L show a variety of accessory attachments that can be attached to an end plug piece 84. These accessory attachments are capable of performing a variety of different functions. For example FIG. 12A shows a end plug piece 84 into which an accessory attachment 92 (comparable to that shown in FIG. 11) has been inserted. The accessory attachment 92 is shown provided with an air inlet/outlet passage device 98 and a connector device 100. FIG. 12B shows an end plug piece 84 provided with a male coupling in the form of a threaded post 102. FIG. 12C shows an end plug piece 84 provided with a male, barbed fitting 104. FIG. 12D depicts an end plug piece 84 into which a threaded male connector 106 is threaded. FIG. 12E depicts a “quick release” fitting 108 (known to the connector/fastener arts) attached to the end plug piece 84. FIG. 12G shows an end plug piece 84 provided with a plugged end piece 110. FIG. 12H depicts the end plug piece 84 provided with a dual air input/output fitting 112. FIG. 121 shows an end plug piece 84 provided with a micro air valve device 114 that includes electrical connector cables 116. FIG. 12J depicts an end plug piece 84 provided with a so-called “cap style fitting 118”. FIG. 12K depicts a base plug piece 84 provided with an accessory 120 having a mounting nut 122, an air input/output fitting 124 and a mounting bracket 126 that can be used in place of a cable harness. FIG. 12L shows the end plug piece 84 provided with an air fitting 128 for air input or release.

[0050]FIG. 13 shows a preferred embodiment of this invention wherein the end plug piece 84 is associated with a cable harness system 130. This particular cable harness system is shown having three cable elements 130A, 130B and 130C. These cable elements are shown connected by a cable connector 132 at the left or forward end of the end plug piece 84. This cable harness system 130 also has a cable connector 134 on the rearward or right side of the base plug device 84. This cable system 130 also is shown having a loop 136 to which mechanical connectors (such as hooks, U-bolts and the like) can be attached. Cable harness systems having four or more cables also can be employed.

[0051]FIG. 14 is a perspective view of the base plus piece 84 and cable harness system 130 shown in FIG. 13.

[0052] Although the preceding disclosure sets forth a number of embodiments of the present invention, those skilled in this art will however appreciate that other arrangements or embodiments, not precisely set forth, could be practiced under the teachings of the present invention. Therefore, the scope of this invention should only be limited by the scope of the following claims. 

Thus having disclosed this invention, what is claimed is:
 1. A fluid-driven tension actuator for converting fluid pressure change into linear motion, said actuator comprising: (1) a tubular sleeve of woven construction, (2) a tubular body of resilient, flexible, elastomeric material that substantially immerses the tubular sleeve and thereby forming an axially expandable tubular body that defines a fluid chamber, and (3) a pair of end plugs that respectively reside in and extend from the tubular body and wherein at least one of said end plugs has an opening that enables fluid communication with the fluid chamber and wherein at least one of said plugs is connected to a mechanical coupling device.
 2. The actuator of claim 1 wherein the tubular sleeve of woven construction is immersed in the body of resilient, flexible, elastomeric material in a central of the actuator.
 3. The actuator of claim 1 wherein the body of resilient, flexible, elastomeric material defines an outer limit to axial expansion of the tubular body.
 4. The actuator of claim 1 wherein the tubular sleeve of woven construction, lies in a center region of the body of resilient, flexible, elastomeric material that substantially immerses the tubular sleeve.
 5. The actuator of claim 1 wherein the tubular sleeve is of a simple weave construction.
 6. The actuator of claim 1 wherein the tubular sleeve is of woven construction is a close mesh network.
 7. The actuator of claim 1 wherein the tubular sleeve of woven construction is a close mesh network defining a configuration of adjacent squares encircling the equatorial region of a fully inflated tubular body.
 8. The actuator of claim 1 wherein each of the two plugs is connected to a coupling device.
 9. The actuator of claim 1 wherein each of the two plugs has a hole in fluid communication with the fluid chamber and is connected to a coupling device.
 10. The actuator of claim 1 that further comprises a clamping device for damping the two ends of the tubular body to a respective end plug.
 11. The actuator of claim 1 wherein the elastomeric material is a latex compound.
 12. The actuator of claim 1 wherein the elastomeric material is neoprene.
 13. The actuator of claim 1 wherein the elastomeric material is a silicon rubber.
 14. A fluid-driven tension actuator for converting fluid pressure change into linear motion, said actuator comprising: (1) a tubular sleeve of woven construction, (2) a tubular body of resilient, flexible, elastomeric material that substantially immerses the tubular sleeve and thereby forming an axially expandable tubular body that defines a fluid chamber, and (3) a pair of end plugs that respectively reside in and extend from the tubular body and wherein each of the pair of end plugs has an opening that enables fluid communication with the fluid chamber and wherein each of the pair of end plugs is connected to a mechanical coupling device.
 15. The actuator of claim 14 wherein the tubular sleeve of woven construction is immersed in the body of resilient, flexible, elastomeric material in a central section of the actuator.
 16. The actuator of claim 14 wherein the tubular body of resilient, flexible, elastomeric material defines an outer limit to axial expansion of the tubular body.
 17. A fluid-driven tension actuator for converting fluid pressure change into linear motion, said actuator comprising: (1) a tubular sleeve of knitted construction, (2) a tubular body of resilient, flexible, elastomeric material that substantially immerses the tubular sleeve and thereby forming an axially expandable tubular body that defines a fluid chamber, and (3) a pair of end plugs that respectively reside in and extend from the tubular body and wherein each of the pair of end plugs has an opening that enables fluid communication with the fluid chamber and wherein each of the pair of end plugs is connected to a mechanical coupling device.
 18. The actuator of claim 17 wherein the tubular sleeve of knitted construction is immersed in the body of resilient, flexible, elastomeric material in a central section of the actuator.
 19. The actuator of claim 17 wherein the tubular body of resilient, flexible, elastomeric material defines an outer limit to axial expansion of the tubular body.
 20. The actuator of claim 17 wherein the tubular sleeve is of a knitted construction is a close mesh network knit. 